Ml 



MOLLUSCA. 



[Nayades. 



Shell very thin, with the hinge line almost straight, and, 

 ascending, forming an angle, from whence it descends in nearly 

 a parallel direction, assuming an obtuse point; anterior side 

 slightly angulated; the basal line arcuated, and descending con- 

 siderably, in consequence of which the posterior side is very 

 deep, being a third more than the anterior one; surface covered 

 with a very bright yellowish-green epidermis, frequently with 

 divergent rays of a deeper hue; ligament not protruding beyond 

 the margin of the hinge line. 



Found in the canal, near Keighley. 

 Variety 6. Complanata, pi. XXVIII,* f. 6, 7. 

 Anodonta complanata, Ziegler Museum ; Rossmassler, I, p. 

 1 12, pi. 3, f. 68, a; Anodonta compressa, Menke, Syn., p. 106; 

 a variety, Rossmassler, IV, p. 24, pi. 20, f. 283; Ziegler Mus.; 

 Anodonta rhomboidea, Schliit. 



Shell very thin, compressed, elliptically-ovate ; the superior, 

 or hinge margin ascending, in a somewhat curved line, to the 

 termination of the ligament, from whence it descends and ter- 

 minates in a produced beak, quite at the lower angle of the 

 posterior side ; basal line very straight, with a slight curvature ; 

 anterior margin rounded, and narrow, near to which the slightly 

 developed umbo is situate; whole surface with concentric wrin- 

 kles, and covered with a reddish-brown epidermis. 



This variety is found in the river Calder, near Wakefield ; 

 and it has been forwarded to me from the Trent, at Repton, 

 near Burton, by the kindness of Sir Oswald Mosley, Bart., a 

 gentleman distinguished for the deep interest which he takes in 

 the advancement of Natural Science. 

 Variety 7. Avonensis, pi. XXIX, f. 2. 

 Mytilus Avonensis, Montagu, Test. Brit., p. 172 ; Turton, 

 Brit. Fau., p. 165; Mytilus Cygneus, var. /3, Maton and Rack- 

 ett, Linn. Tr, VIII, p. 1 10, pi. 3 a, f. 3 ; Fleming, Edin. Ency., 

 VII, p. 99, pi. 206, f. 5 ; Anodonta Anatina, var., Rossmassler, 

 VI, p. 57, pi. 30, f. 418. 



Shell ovoid, or subrhomboidal, ventricose, rather thick, in 

 some specimens very thick ; anterior margin rounded, short ; 

 posterior margin long, and pointed ; hinge line subarcuated ; 

 basal line slightly curved; external surface generally rough, with 

 sharp concentric wrinkles, covered with a very thick, variously 

 coloured, rather dull epidermis ; sometimes olivaceous, and at 

 others reddish-brown. 



This variety is subject to considerable variation of form and 

 size, and is in general well marked. It is usually of a dull 

 white internally, with but little of the pearly lustre so prevalent 

 in its congeners. 



Found in the Avon and New River; also near Tisbury, Wilt- 

 shire; the Trent, near Burton; near Steeton ; the canal, near 

 Halifax, and of a large size in the canal, near Sowerby Bridge, 

 Yorkshire. 



Variety 8. Ponderosa, pi. XXX, f. 1,2, and pi. XXIX, 

 f. 3. 



Anodon ponderosa, Pfeiffer, II, p. 31, pi. 4, f. 1 to 6; Ross- 

 massler, IV, p. 24, pi. 20, f. 282 ; Mytilus Cygneus, var. p, 

 Maton and Rackett, Linn. Tr., VIII, p. 109, pi. 3 a, f. 3. 



Shell large, thick, ponderous, rhombic-oval, very ventricose ; 

 externally wrinkled ; with the epidermis rough, fibrous, and 

 semivillous at the rounded anterior extremity, and at the base; 

 posterior side long, subrostrated, and subtruncated at its extre- 

 mity ; base but slightly bent, or nearly parallel; hinge line 



considerably arcuated, with a long ligament, from whence it 

 somewhat abruptly descends ; beneath the ligament a sinuated 

 groove, rising abruptly, and forming a ventricose disk; umbones 

 rather tumid, and decorticated; the ligamentary sinus small, 

 subcordate; inside bluish-white. Length two inches and three- 

 eighths ; breadth four inches and five-eighths ; thickness two 

 inches and a half. 



I was favoured with this interesting variety by my friend Mr. 

 Henry Johnson, Curator of the Museum, Royal Institution, 

 Liverpool, who found it at Otterspool, Aigburth, on the pro- 

 perty of John Moss, Esq., who has since most kindly supplied 

 me with a complete series for investigation. It also occurs in 

 Loch End, near Edinburgh. Another handsome variety of this 

 shell inhabits the lake at Rolleston, the seat of Sir Oswald 

 Mosley, Bart., near Burton-upon-Trent, to whom I am indebted 

 for a fine series. 



The latter variety is somewhat more acuminated in the beak- 

 ed side, and devoid of the villosity of the Otterspool variety, in 

 which respect it agrees with that found at Loch End. 



This shell has been mistaken for the A. Avonensis, by some 

 British Naturalists. It is, however, considerably more inflated, 

 in proportion to its size, and a third larger. 

 Variety 9- Subrhombea, pi. XXX, f. 3, 4. 

 Anodon subrhombea, Brown, MSS. ; Anodonta piscinalis, 

 var.? Rossmassler, VI, pi. 30, f. 416. 



Shell thick, subrhomboidal, rather inflated ; anterior side 

 slightly produced ; hinge line nearly parallel, and ascending 

 towards the posterior side ; ligament long, subarcuated, from 

 whence it suddenly declines towards the somewhat truncated 

 extremity ; basal line considerably arcuated ; exterior surface 

 but slightly wrinkled transversely ; umbones small, and acute ; 

 inside bluish-white, with faint pearlaceous reflections. 



This variety differs from the A. piscinalis, in being more 

 ponderous, and more inflated, in the hinge line being more 

 arcuated, and in being less rostrated. 



Found in the Irwell, near Manchester, by my esteemed 

 friend Mr. Samuel Gibson, of Hebden Bridge, Yorkshire ; to 

 whom I am indebted for specimens. 



Variety 10. Piscinalis, pi. XXVIII,* f. 3, 4, 5. 

 Anodonta piscitialis, Nilsson, p. 116, No. 3 ; Drapernaud, 

 Hist, des Moll., pi. 12, f. 2 ; Rossmassler, IV, p. 23, pi. 19, f. 

 281 ; Anodonta ventricosa, Pfeiffer, II, p. 30, pi. 3, f. 6; Alder, 

 Mag. Zool. and Bot., II, p. 118; wood cut, Kenyon, Mag. Nat. 

 Hist., I, f. 188; Mytilus maculatus, Sheppard, Linn. Trans., 

 XIII, pi. 5, f. 6, young shell. 



Shell subovate, ventricose, thick ; hinge line ascending in a 

 waved, subarcuated sweep towards the posterior side, and des- 

 cending in a hollow bent line, ending in a produced, turned 

 upwards beak ; basal margin considerably arcuated, and ascend- 

 ing rather abruptly towards the posterior side ; outer surface 

 covered with a thick, shining, olivaceous epidermis, with many 

 obscure, radiating lines of a darker hue. 



Found in the canal, near Birmingham ; and in Combermere, 

 Cheshire, where I procured an extensive series, while on a visit 

 at the Abbey, through the polite attention of Viscount and 

 Lady Combermere. 



Variety 11. Rostrata, pi. XXVIII,* f. 8, 9- 

 Anodonta rostrata, Kokeil Museum; Rossmassler, IV, p. 25, 

 pi. 20, f. 284. 



